You have some unknown integer

, and you know that adding this and the next two integers,

and

, gives a total of 57.
This means

The task is to find all three unknown integers. Notice that if you know the value of

, then you pretty much know the value of the other three integers.
To find

, solve the equation above:

So if 18 is the first integer, then others must be 19 and 20.
Answer:
acute angles
Step-by-step explanation: sorry i couldnt answer the other one
Since 57x17=969 I did 969-942 and got 27 so there is 16 full rows and then 27 left over so that means it won’t be a full row but 27 extra seats will be filled. (If your wondering where the 17 came from that’s how many rows can be made that’s over 942 because if I did 57x16 it would equal 912 and I would not have had a full row of chairs)
x=-y/3 +9 i believe that should help you